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Sunday, 14 March 2010

I’m a Gibsonian. I study perception and action from an ecological perspective, which is based in James Gibson’s theories of perception (and Nikolai Bernstein’s theories of motor control). This perspective is, in many ways, in direct conflict with the dominant cognitive paradigm in psychology, and frankly a lot of people simply think it’s ridiculous. This is partly our own fault: the ecological camp is small, a bit insular and prone to picking odd fights. But I think we are right, even if sometimes I don’t think we’re studying it or talking about it right. My goal for this blog is to work some of these thoughts out (amongst other things) so I can actually turn these thoughts into experiments and papers.

The main driver for me doing this right now is an internal argument that is brewing amongst ecological types that I think is a) flawed and b) a waste of time. I’ve been thinking and talking about this conflict for a little while now, but I need to find ways to go after the flaws empirically: I am a scientist, and in spite of all the evidence I really do believe psychology can be a science. The argument is actually yet another round of the only argument that ever happens about perception: what constitutes information for a perceiving organism? The modern Gibsonian approach makes specific claims about this, so before we get into the recent stuff we need some context. That means we need a little history.

A Little History

The fundamental question in perception is, what is the information for perception? What is the form of the proximal stimulus (the thing that actually causally interacts with an organism’s sensory apparatus)? The answer to this question has almost always been that the proximal stimuli are sensations, meaningless physical events (photons for vision, compression waves for hearing, etc). Sensations are meaningless because they do not fully specify the world that caused them; they are ambiguous, because a given physical event gives rise to many patterns of sensations (a small red ball flying towards you produces a different optical pattern than, say, a large blue ball, although they are both the same type of event).

The basic ‘sensation based theory of perception’ runs as follows:

a.Something happens in the world (the distal stimulus). This is what an observer eventually needs to respond to, and so needs to detect it somehow.

b.This event causes a pattern of change in the light, although this pattern only correlates with the event in the world; local conditions, the observer’s perspective, etc, alters many of the details.

c.An observer detects this pattern (the proximal stimulus) which is related to the event in the world but not uniquely.

d.They must then infer what event in the world lead to this pattern (i.e. resolve the ambiguity).

e.The observer then responds appropriately to the event.

Modern cognitive psychology has what is essentially just the latest version of this hypothesis, in which it fills in some of the details. (a) and (b) remain the same: these are taken to be the facts of the matter (and it’s the correlation aspect in (b) that Gibson will object to):

c.The proximal stimulus (for vision) is the ‘image’ projected to the back of the eye, onto the retina. Like a camera, the eye focuses rays of light (photons) to a point (the fovea) and forms an image. The image isn’t really a picture (not in modern theories, although people still talk about the retinal image); it’s a pattern of light distributed across the retina. There are internal correlations between the ‘pixels’ such that neighbouring pixels tend to resemble each other, unless there is an edge, in which case they differ immensely (telling you there’s an edge there). However, this image is ambiguous with respect to what caused it; there is a one-to-many mapping, in which one event could lead to multiple patterns (every visual illusion is an example of this).

d.The job of vision is to resolve this ambiguity, via inference. Essentially, the solution to this problem is that the visual system must make an educated guess about which of the ‘many’ possible events caused the ‘one’ proximal stimulus. The education of the guess comes from mental representations, the workhorse of cognitive psychology. A representation is a pattern of neural activity/connections that ‘stands in for’ (i.e. represents) the missing information. The representation may contain information about past exposure to this pattern and what the event turned out to be (learning); it may contain information about how certain types of correlations tend to indicate one thing or another. Visual perception is the cognitive process of detecting the proximal stimulus, then selecting and applying the correct representations from your repertoire to resolve the ambiguities.

Cognitive theories about visual perception therefore

1.assume a poverty of stimulus, i.e. an ambiguous proximal stimulus that must be enriched with internally stored information, and

2.are about uncovering the contents of the representations and how the correct one(s) are selected and used.

This is the state of things today, and is the essential form of the argument that James Gibson rejected with his theories. Gibson’s move was simple: he considered (b) from above, and rejected it. If the proximal stimulus only correlates with events in the world, he said, then perception is doomed to failure – how do we ever build correct representations? How could we possibly select the right ones? Gibson’s solution was to rethink information, and propose that events in the world can, in fact, lead to changes in patterns of light that uniquely specify the event that caused them, rather than merely correlate with. He also argued that it couldn’t be any other way, if perception was to ever work the way we experience it working every day. The next step is to consider some details of Gibson’s alternative.

9 comments:

As a medical doctor, I did not know, or cared, much about the different theories of perception. But now as a Neuroscientist, it's nice to see all the sides of the coin. Meaning, I'm interested.

I would agree with Gibson's direct realism in most ways because of my background, however, I wouldn't know if it fits my pain research.I'll elaborate; what we know so far about pain perception is that it is a two fold phenomenon that depends on the physical perception of the stimulus and its recognition as "painful", which is transmitted from the site of the stimulus to the brain. The perception of the stimulus as painful also depends on a top-down network which can either "increase" or "decrease" said "pain", or give it a different quality. This top-down pathway is said to be influenced by cognitive mechanisms (reappraisal, attention, and expectation). Pain can also be "created".Therefore, looks as if pain perception depends highly on cognition.

I know pain is a very discussed and controversial topic, but I would like to know your opinion about that within your framework as Gibsonian.And what about Ecological studies of pain? this concept is alien to me.

Pain is an interesting example. It's never talked about the in the general perception literature, we always think about things like vision and hearing. Gibson talks a little in the '66 book about it, mostly how it'd been thought of as a subdivision of touch (which he was interested in redefining as the active process of haptics, anyway)

My guess is that pain, per se, doesn't fall under this theory, because it is never specific to the distal stimulus. You can get the same pain from multiple sources (many to one) and different pain from the same source (one to many) so it just isn't working according to a specification relation. This is fine, because what it's for doesn't require this level of precision.

I'll get round to smacking down neuroscience too, though, so stay tuned :)

Any thought on Barsalous (and others) embodiment ideas? (I'm reading the Chemero book you raved about, so I'll have more to consider whenever I have time to actually read and not lecture), but I'm very fascinated by the embodiment theories, and I have always thought fondly of Gibson, although I never had much chance to delve into him. Plus, you know, dynamical systems, chaos and all that fun stuff....

I'm familiar with Barsalou. He seems to have his heart in the right place, but he still assumes computational, symbolic processing via representations. He argues that representations are grounded in perception, rather than just being abstract symbols. So, representations as "perceptual symbol systems." First, this account is still fundamentally computational and relies on discrete representations. Second, when he refers to perception, it's in terms of the "sensation" explanation that Andrew mentions (that sensations don't fully specify their referents and we use representations to resolve the ambiguity). So, Barsalou updates the presumed content of symbolic representations to address specific theoretical problems with abstract symbols (like the symbol grounding problem), but he does this without having a good background in perception.

Barsalou updates the presumed content of symbolic representations to address specific theoretical problems with abstract symbols (like the symbol grounding problem), but he does this without having a good background in perception.If I had a dollar for every psychologist for whom this is true, I'd have $375.16 :v

I'm going to get into this too, but Barsalou is just falling for the main problem with cognitive psychology, namely he's assuming representations and just being snazzy with their contents. Chemero's classification system for theories (radical vs not, embodied vs not) is handy, I think, for sorting out the completely predictable proliferation of versions of embodied cognition.

Thanks so much for your thoughts and connections to other resources. I am a social scientist (I guess you'd say) and have been learning about and enjoying ecological psychology for a number of years. I am particularly taken by the general concept of the affordance. More recently I have been reading the work of GH Mead and am intrigued with his notions of contact experience and distance experience to articulate the difference that language has made on the sensory surround for humans. The Philosophy of the Act (Mead, G. H., (1938). The philosophy of the act. Chicago: Ill., University of Chicago Press.) is a great source for more specific discussion. Essentially Mead reasons that language could only evolve out of an embedded and embodied continuously connected organism. Much of Mead's work (along with Dewey and others) is resonate with Gibson and Barker's visions of a psychology based on direct experience. I am most interested in the relationship between the epistemology of perception as it relates with non-dual theories of space/time, self/other, and most recently matter/meaning (see Barad, K. M. (2007). Meeting the universe halfway: Quantum physics and the entanglement of matter and meaning. Durham: Duke University Press.)Anyway, thanks so much and I will read your blog regularly.Chris

Hi Chris, and welcome! I think you are the first reader we have who I don't already know :) How did you find us?

I don't know Mead, although anyone doing embodied cognition in the 30s will be worth looking up.

I think you might enjoy the summaries and comments I'm going to work up on the Heft book (see the 'reading group' post); he's already distinguishing Gibson as specifically non-dualist, which of course he had to be as a direct realist. I'll post the first few notes in the next day or so when I have some time to organise my thoughts.

Just a note to bring your attention to this post - somehow the html for the bullet lists is broken. At least I'm seeing (on Internet Explorer 8) chunks of markup in the text, such as "<!--[if !supportLists]-->a. <!--[endif]-->".

Nice catch! I made this post in Word and copied over before I learned that this brings a lot of dodgy HTML along with it. Firefox reads it fine so I've never gone back to edit it, but if it's properly broken in IE I may do it!